powerpc/mm: Rework context management for CPUs with no hash table

This reworks the context management code used by 4xx,8xx and
freescale BookE.  It adds support for SMP by implementing a
concept of stale context map to lazily flush the TLB on
processors where a context may have been invalidated.  This
also contains the ground work for generalizing such lazy TLB
flushing by just picking up a new PID and marking the old one
stale.  This will be implemented later.

This is a first implementation that uses a global spinlock.

Ideally, we should try to get at least the fast path (context ID
already assigned) lockless or limited to a per context lock,
but for now this will do.

I tried to keep the UP case reasonably simple to avoid adding
too much overhead to 8xx which does a lot of context stealing
since it effectively has only 16 PIDs available.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/include/asm/mmu-40x.h

@@ -54,8 +54,9 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned int	id;
+	unsigned int	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 
 #endif /* !__ASSEMBLY__ */

arch/powerpc/include/asm/mmu-44x.h

@@ -56,8 +56,9 @@
 extern unsigned int tlb_44x_hwater;
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned int	id;
+	unsigned int	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 
 #endif /* !__ASSEMBLY__ */

arch/powerpc/include/asm/mmu-8xx.h

@@ -137,7 +137,8 @@
 
 #ifndef __ASSEMBLY__
 typedef struct {
-	unsigned long id;
+	unsigned int id;
+	unsigned int active;
 	unsigned long vdso_base;
 } mm_context_t;
 #endif /* !__ASSEMBLY__ */

arch/powerpc/include/asm/mmu-fsl-booke.h

@@ -76,8 +76,9 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
-	unsigned long id;
-	unsigned long vdso_base;
+	unsigned int	id;
+	unsigned int	active;
+	unsigned long	vdso_base;
 } mm_context_t;
 #endif /* !__ASSEMBLY__ */
 

arch/powerpc/include/asm/tlbflush.h

@@ -29,6 +29,8 @@
 
 #include <linux/mm.h>
 
+#define MMU_NO_CONTEXT      	((unsigned int)-1)
+
 extern void _tlbie(unsigned long address, unsigned int pid);
 extern void _tlbil_all(void);
 extern void _tlbil_pid(unsigned int pid);